The present invention relates to tanks equipped with a venting plug, and more particularly to a vapor bypass tube mounted to a fuel tank in cooperative relation to a venting pressure relief device.
FIG. 1 depicts a typical application of a fuel tank 12 with respect to a truck tractor and semi-trailer rig 10. FIG. 2 is a detailed view of the fuel tank 12, which includes a tank body 14, a removable filler cap 16, and a melt plug 18, which is the prior art solution for providing a venting pressure relief device. As shown in FIG. 3, the melt plug is sealingly connected to the tank body 14, and is composed of a low melting point metal (lower than that of the metal of the tank body), such as for example a lead alloy installed at the top of the tank. In operation, heat will soften the melt plug, and increased pressure in the tank will cause it to be dislodged.
The present invention is a venting system for a fuel tank in the form of a vapor bypass tube which is interfaced with a pressure relief device (ie., a melt plug) such that the bypass tube provides vapor pressure bypass of the melt plug hole.
A fuel tank is provided with a pressure relief device integrated with respect to the tank. A vapor bypass tube has a first end sealingly mounted to the tank body circumscribably in relation to the pressure relief device. The vapor bypass tube has a second end, opposite the first end, which is open and located deep inside the tank. A vent aperture is provided in the vapor bypass tube adjacent the first end which provides vapor displacement from within the vapor bypass tube when the tank is being refueled.
In operation of the vapor bypass tube according to the present invention, in the event a fuel tank equipped therewith has fuel thereinside, is inverted, and the pressure relief device has been actuated (for example by the melt plug having dislodged), vapor above the fuel passes through the vapor bypass tube to thereby vent the tank so as to prevent vapor pressure build-up. On the other hand, if the tank remains upright and the pressure relief device is actuated, the vapor may easily vent through the vapor bypass tube in situations where the fuel level is below the second end of the vapor bypass tube vent; in situations where the fuel level is above the second end of the vapor bypass tube, the aperture will allow vapor to vent and fuel and/or vapor may be expelled through the vapor bypass tube.